Multiple step switch



April 11, 1950 w0, SCHUL-rz 2,503,888

MULTIPLE STEP SWITCH Filed Jan. 21, 1949 2 Sheets-Sheet l INVENTOR. M//fawf 0 {wzl/7 BY EM y@ Plil 11, 1950 w. o. scHuL'rz 2,503,888

' A l MULTIPLE STEP SWITCH Filed Jan. 21, 1949 2 sheets-sheet 2 Patented pr. 11, 18950 MULTIPLE STEP SWITCH William 0. Schultz, Marshfield, Wis., assignor to McGraw Electric Company, a corporation of Delaware Application January 21, 1949, Serial No. 71,966

2 Claims. (Cl. 201-48) This invention relates to a multiple step switch and is particularly directed to a multiple step switch which is designed to connect capacitors in a power line for power factor correction.

Objects of this invention are to provide a novel form of multiple step switch which is so made that it will prevent excessive rush of current when'capacitors are connected to the power line, which has a quick break when the capacitors are successively disconnected from the line, and which has means for limiting the inrush of current during the connecting of the capacitors to the line and which also acts in a manner to assist in suppressing the final arc when the capacitors are successively disconnected from the line.

It has been found that when capacitors are disconnected from the line, there is frequently a tendency for the arc to persist as each capacitor is disconnected from the line, and a still more serious condition exists when capacitors are connected to the line. In view of the nature of the capacitors, it is apparent that when a substantially uncharged capacitor is connected to the power line there is normally a very severe inrush .of current and this inrushbecomes more severe as successive sections or banks of capacitors are connected into the line, for the previously charged capacitors will increase the current rush to the uncharged additional capacitors as they are successively connected to the line. These effects produce rapid burning away and wearing off of contacts, although the contacts are submerged in oil.

This invention is designed to overcome the above noted defects and objects of this invention are to provide an effective multiple step switch which limits the inrush of current in a marked manner when additional capacitors are successively connected to the power line, and which also greatly reduces the tendency of the are to "hang on or persist when the capacitors are successively disconnected from the line and to secure these results in a very simple manner by providing an impedance as a unitary structure with the rotary portion of the multiple step switch, and to so associate this impedance with a short-circuiting device that the impedance may be shorted out whenever necessary in an automatic manner and may be inserted during the connecting of capacitors into the line and may be again inserted at the instant thatthe capacitors are being disconnected from the line.

Embodiments of the invention are shown in the accompanying drawings, in which:

Figure'l is a fragmentary, sectional view of a. multiple step switch.

Figure 2 is a fragmentary view showing the position of the parts as the rotor is moving towards disconnecting position with reference to one of the auxiliary terminal assemblies.

Figure 3 is a view corresponding to Figure 2 showing a successive position of the rotor just after that illustrated in Figure 2.

Figure 4 is a view showing the manner in which an auxiliary terminal assembly is initially connected to the main contact of the rotor with the impedance temporarily inserted.

Figure 5 is a fragmentary view showing a further form of the invention.

Figure 6 is a diagrammatic view showing the manner in which a multiple step switch may be employed to connect a bank of capacitors to a three phase power line.

Referring to the drawings, it will be seen that the multi-ple step switch is enclosed in a cylindrical housing l which is provided with an internal, insulating sheath 2 and with an insulating, cylindrical supporting portion 3. This in# sulating supporting portion 3 carries a main terminal 4 and a plurality of auxiliary terminal assemblies 5, each of the latter including a resliently mounted contact or switch arm 6 which is spring pressed towards the rotor indicated generally by the reference character l, the rotor 1 being rigidly carried by a metal shaft 8. If desired, three sections of the switch may be employed, one only having been shown in Figure 1L The three sections of the switch are employed when a three phase power line is to have power factor correction. The shaft 8 is driven in any suitable manner by means of an automatically controlled motor mechanism, which latter is well known in the art, and is not illustrated.

The shaft is provided with an insulating sleeve 9 which is secured rigidly to the shaft by means of a metal pin I D. The rotor consists of an insulating cylinder block or main portion Il which is secured to the insulating sleeve 9 by means of a set screw I2. This main insulating block or main body portion of the rotor is provided with a contact rail or main extended contact i3 which is connected by means of a flexible conducting leader or ribbon ld with the main terminal 4, the end of the Contact rail I3 being preferably rounded as indicated at I5 to avoid damaging' the flexible ribbon I4 when the rotor is rotated in a counterclockwise direction as viewed in Figure 1.

The rotor is provided with an impedance indicated at I6 which may take the form of a wire resistor which in turn may be carried by an insu1ating,grooved spool I1. The impedance which in the form shown for the resistor i6, forms a unitary portion of the rotor as is apparent from an examination of Figure 1. One end of the resistor or impedance i6 is connected directly to the main-p circular or. arcuate contact I3 and the other end of thel impedance I- isl connected to a metal bracket I9. This metal bracket is provided with an auxiliary rotor contact or switchi arm 20 which is spring pressed in a countercloclsz;A wise direction as viewed in Figure 1 and which is pivotally carried by the bracket;l 9. An adjust able stop 2| is provided forlimiting the counter clockwise rotation of the auxiliary rotor contact 20 and preferably a flexible conducting leaderon ribbon 22 is connected between the metal bracket I9 and the auxiliary rotor contact or auxiliary rotor switch arm 2U. contact. 23= isI carried, by; a spring arm 24 electrically connected to the; main rotorV contact l3iar1dS. adapted' t0: bei engaged byV a contact., 25 carriedby.V a projection. ofthe. switch arm 2.0 when the switch arm 20 is: rocked in: aclockwise directionv to. the positionshown, for'instanceg. in Figure 2; Thesercontacts25-and 23 are designed to shortfcircuit the impedance: t8: when such contacts are in engagement with. each otheru as is; obvious from aninspection of Figure. 2; o Y E11-cinl reterenceto Figure, 6, it will be seen that the auxiliary terminals 5 or terminali: assemblies are designed to be connected; to a. plurality.r of capacitors 2.(gand1theA maine. rotor contact i3; is designed to be connected at a neutral point-11 for a-.threephase system for instance. Itisapparent that aszthe.- roto-ris moved from the.' position shown. in, Figure 1` in a rcounter-- clockwise direction, that one or.. more ofl the. caf Vpacitors or capacitor banks will be. cut out' or disconnected,l fromthe; power line indicated gen'- eralIy by` the. reference lcharacter 28. Ifr itis desired, to.. disconnect.v one or the capacitors.- of each set. from thepower line, the: rotor isv moved ina.co11nterclockwise direction so as todis.-` connect. the main stationaryterminal'. Il'4 from the last auxiliary. terminal assemblyI 5.as; viewed. in

Figure 1.` As the rotor movesina counterclock wise. direction the auxiliary Contact. arm` Gl will pass from themainrotorcontact. i3 andywill: enf.

gagev the auxiliary rotor contact or switch arm 2-0. andcontinuedfrotatmn ot, theI rotor will short outtheresistor IB., as shown in Figure 2. Thus the resistor is not. called...upon to. carry current for. any material length of. time, during this dis.- connecting operation. Continued. rotation ofthe rotor will, cause. the auxiliary rotor contact or, Switch .arm 2.0 to move.V awayfrom the; auxiliary switch arm or contact. 6i -of'the'auxiliary contact assembly 5. as showm for instance,V inF-igLu-e 3; and this disconnection will. occur lwith as'nap action dueto the spring 2S.: of the auxiliary'rotor contact 24J which causes the rotor'cont'act-IZD to rock in a countercloc'vkwisefdirection tothev positionx shown in Figure '3. rIhis motion: oi the auxiliary., rotor contact (2i). immediately reinserts the resistor lli andmateri'ally assistsin'suppress` ing any arc that maytendt'o nersistat. this. final break.. Further, it is to be noted that the break isV a quick break asl will. be obyiousfrom a comparisongof FiguresZ `and3.. Under these conditions thereisvery little wearonfthe contact arms. of the stationary auxiliary contacts. or ,of the rotor contacts. The contact arms aswell as the. main contact. are made of. high arc. resisting metal of any suitable type so as to materiallyl prolong the life of the device and all of the contacts are arranged to operate submerged in oil in accordance with the usual practice.

It is to be noted upon examination of Figure 4, for instance, that when the rotor is rotated in a clockwise direction to connect a capacitor to theA powerg line, that the first contact is made between the auxiliary rotor contact or rotor switch arm 20 and the corresponding auxiliary terminal switch arm 6 with the resistor I6 connected between the main contact I3 of the rotor and the auxiliary rotor contact 20. This resistorlimits*` the inrush of current which is very pronounced under" normal conditions and which would rapidly Vdestroy the contact or switch arms in the absence. of, the impedance or resistor I6. This impedance limits the inrush of current to aisafe; value which will not damage the switch arms. It is apparent that as more and more capacitors, are,- connectedE tothe power line. that the inrush current condition becomes more and more. severe asg the4 charged; capacitors. tend` tu greatly increase the current rush tc.- the unf charged new capacitor that.4 is being; connected toA the; power line. However, the resistor. LG is so: chosen as;y toholdI the current value down! to such afpointthat nomaterial damage is donerto the. cont-act. armsV evenf` under the most. adverse conditions. as hereinabove pointedl out.. Continued motion of the, rotor directlyv connects the auxiliary; switch arm 6. to-the.n^iai1rroln r contac i3 asshown in Figurel., V A 5 In the. modifiedY form. of the invention; shown in.Eigure 5, the viexible-y leaderllt of. Figure l is dispensed with and instead the main terminal' 4f is permanently` connectedv with the: main. rotor contact I3! by means of a. main resiliently, mounted switchv arm. titl.V Y

n litwi'll be; seen that ai novelrform of multiples/Gn switch. hasbeen-provided which is highly; successful even when usedy under the severe conditionsof. connecting capacitors to;v a `high ten.- sion power line for power factor Correction.

YIt` will beseen further that. the multiplefstep; switch, though having; this.: desirable.- characterise tic; is nevertheless` of. simple. constructionrand mayl beffsafelyfand; readily produceda.

Although this: invention. has; beenrdescribedr considerable detail, it is: to; be; understoodithat such. description-.iis intended as'illustrativerrathen thanflimiting, as thexinventionimaybe variously embndied 'andis to: bie interpreted; asfclainred.

I claim:

V'1'. A. multiple step'. switch'comprising afmain terminal', a plurality of auxiliary-terminal. assem-x blies; a. rotor, anf extended main `rotor contact. arranged to successively Vengage and disengage said` auxiliaryy terminal 'assemblies as saidffrotr isl'rotat'ed Ain switch closing and switch opening; directions, respectively; and beingconnected-"tof said main terminal, av movablefaulxiliary rotor' Contact carried'l by` said rotor;` an iinpedancei'oo'nnected betweeny Vsaid niaing and: auxiliary 'rotn'rj contacts; said` auxiliary rotorcontactbeingrposi;

tioned'" in trailing, relation to said` main' rotor contactwhen said rotor. isinovingj towards switch'. openingA position and being arranged to tempo* rariily engage` an auxiliary terminal. assembly' after said 'main` rotor` contact has. become. disenfgfagedl therefrom,r andfbypass; switch means com` trolled by, said auxiliary rotor contact. for tem porarilyvv by-'passing, said impedancegand tonfremoving the. by-pass when. 4said;aumliary.y rotor Contact moves away from the last mentioned auxiliary terminal assembly.

2. A multiple step switch comprising a main terminal, a plurality of auxiliary terminal assemblies, a rotor, an extended main rotor contact arranged to successively engage and disengage said auxiliary terminal assemblies as said rotor is rotated in switch closing and switch opening directions, respectively, and being connected to said main terminal, a movable auxiliary rotor contact carried yby said rotor, an impedance connected between said main and auxiliary rotor contacts, said auxiliary rotor Contact being positioned in trailing relation to said main rotor contact when said rotor is moving towards switch openincr position and being arranged to temporarily engage an auxiliary terminal assembly after said main rotor contact has become disengaged therefrom, and by-pass switch means controlled by said auxiliary rotor contact for temporarily by-passing said impedance and for removing the by-pass when said auxiliary rotor 6 contact moves away from the last mentioned auxiliary terminal assembly, said auxiliary rotor contact being spring biased and having a quick break with reference to said auxiliary terminal assemblies.

WILLIAM O. SCHULTZ.

REFERENCES CITED The following references are of record in the ile of this patent:

UNITED STATES PATENTS 

